Hydrothermal and solvothermal reactions have drawn attention as means for synthesizing compounds. For example, JP Patent Publication (kokai) No. H11-288732 A (1999) discloses a method for preparing zinc sulfide particles having multiply twinned structures and an average particle diameter of 5 nm to 20 μm via a hydrothermal reaction of a sulfur ion and a zinc ion using water as a reaction solvent at 150° C. to 370° C. during the process of particle growth.
Various chalcogenide compounds have drawn attention as alternatives to existing expensive platinum catalysts. Catalysts used for polymer electrolyte fuel cells are mainly platinum and platinum-alloy-based catalysts. Specifically, catalysts in which a platinum-containing noble metal is supported by carbon black have been used. In terms of practical applications of polymer electrolyte fuel cells, one problem relates to the cost of materials. A means to solve such problem involves the reduction of platinum content.
Recently, low-cost fuel cell catalysts have been developed via a reaction that produces water as a result of four-electron reduction of oxygen, which results in elimination of the need for expensive platinum catalysts. Electrochimica Acta, vol. 39, No. 11/12, pp. 1647-1653, 1994 discloses that a catalyst comprising a chalcogen element is excellent in terms of four-electron reduction performance and suggests that such catalyst be applied to fuel cells. Specifically, Electrochimica Acta, vol. 39, No. 11/12, pp. 1647-1653, 1994 discloses a Mo—Ru—Se ternary electrode catalyst and a method for synthesizing the same.
Also, JP Patent Publication (kohyo) No. 2001-502467 A discloses, as a platinum (Pt) catalyst substitute, an electrode catalyst comprising at least one transition metal and a chalcogen. An example of a transition metal is Ru and an example of a chalcogen is S or Se. It is also disclosed that, in such case, the Ru:Se molar ratio is from 0.5:1 to 2:1 and the stoichiometric number “n” of (Ru)nSe is 1.5 to 2.
Further, JP Patent Publication (kohyo) No. 2004-532734 A discloses, as a Pt catalyst substitute, a fuel cell catalyst material comprising a transition metal that is either Fe or Ru, an organic transition metal complex containing nitrogen, and a chalcogen component such as S.
Further, J. Chem. Soc., Faraday Trans., 1996, 92 (21), 4311-4319 discloses Ru—S, Mo—S, and Mo—Ru—S binary and ternary electrode catalysts and methods for synthesizing the same.
Further, Electrochimica Acta, vol. 45, pp. 4237-4250, 2000 discloses Ru—Mo—S and Ru—Mo—Se ternary chalcogenide electrode catalysts.